FIGS. 8 and 9 depict an example of a conventional LED lamp including LEDs as the light source (see, for example, patent document 1). The LED lamp X shown in these drawings includes a plate-shaped substrate 91, a plurality of LED modules 92 mounted on the substrate 91, a heat dissipation member 95 attached to the substrate 91, a case 93 that encloses therein the substrate 91, and a terminal 94. An interconnect pattern (not shown) connected to the LED modules 92 and the terminal 94 is provided on the substrate 91. The LED lamp X is configured to cause the plurality of LED modules 92 to emit a light upon fitting the terminal 94 to an inlet of a socket for a home-use fluorescent illumination instrument.
Here, the home-use fluorescent illumination instrument refers to an illumination instrument mainly used for general interior illumination, more specifically to an illumination instrument that utilizes, for example in Japan, the commercial power supply of 100 V, and is compatible with a straight-tube fluorescent lamp according to JIS C7617 or a circular fluorescent lamp according to JIS C7618.
The light from the LED module 92 presents such a light distribution that a majority of the light concentrates in a main emission direction indicated by arrows pointing upward in FIG. 9. Accordingly, the LED lamp X is normally attached such that the main emission direction is oriented toward a floor opposite a ceiling 96. However, a portion of the light from the LED module 92 travelling opposite the main emission direction is blocked by the substrate 91. Thus, the LED lamp X has a drawback in that the ceiling 96 remains dark compared with a situation where the home-use fluorescent lamp is turned on.